Molly Peterson

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This story is part of our summer series "Beachcombing," in which KPCC reporters will explore the ecology, economy and culture of Southern California's beaches and coast. Let us know what you think in the comments below or on KPCC's Facebook page.

The natural processes that bring sand to most beaches in Southern California have been disrupted by development and other human activities.

"Beach nourishment" projects are replacing some of that sand, primarily on beaches in L.A. County. But the efforts are replacing only about half of what is lost each year.

Therese Adolfson isn't thinking about beach erosion as she enjoys a summer day on the sand of Venice Beach.

"It’s really soft. And hot. It’s great," she laughs.

Adolfson's husband and two daughters are tearing into a fried chicken lunch, sitting on a blanket next to her. They are visiting from Sweden, answering the call of California’s coast. She calls Venice Beach "one of our major stops."

The golden-white sands of Venice have long sold the Golden State dream. In 1939, the people who picked Miss California picked the Venice boardwalk as the place to do it.

The problem is, humans have been trying to augment Venice’s beauty.

A beach is born at the point where a wave crashes on the shore. It delivers sand, and creates more as it pounds and tumbles rocks. UCLA geographer Tony Orme uses the British term for the area where this happens: "the swash zone."

"It’s onamatopeic, you see, sounds like what it is, swash, swash, runs these pebbles up the beach, you see, and then when water runs back down the beach, it moves these materials as well, then you get the backwash...and so on," he says, chuckling.

Over the last century, as we’ve developed the coast, we’ve changed what goes into the swash zone, and in so doing, changed a lot of California's beaches.

For one thing, Orme says county officials wanted to make it easier to get to local beaches, and safer to use them.

"For a while, we used to build hard structures, groins, sea walls, jetties, breakwaters," says Orme, pointing out that Venice Beach has a breakwater at its north end. "They for the most part don’t work very well at all."

What Orme means is that the man-made walls reflect waves away from the shore, depriving the beach of sand.

At the same time, foothill development starved Venice and other beaches of their historic source of sand. Normally rocks, boulders, and debris would flow downriver from local mountains after a storm.

But Jon Warrick of the U.S. Geological Survey said that changed when cities acted to protect people and property in the mountains from stormwater runoff.

"There’s a whole bunch of debris basins and dams up in the mountains that capture that sand, and it never gets to the beach," says Warrick. "And so there’s one way the watersheds are providing an important resource – sand – to the coast – and yet we have altered that."

All these alterations mean beaches have been eroding for decades – and growing more vulnerable to big storms. Carol Baker, spokeswoman for L.A. County Beaches and Harbors, recalls one storm that pummeled Venice 30 years ago.

"The parking lot in Venice Beach was destroyed. The bike path was destroyed," says Baker. "So it was a very significant storm and it caused damage all the way up to Santa Monica and beyond."

That kind of threat prompted L.A. County to drop $1 million on Venice’s most recent facelift.

"We took 30,000 cubic yards of sand from the northern part of the beach and hauled it down to this area that was more narrow and in greater jeopardy," says Baker.

That's a form of beach nourishment, which involves redistributing sand that’s pulled from the ocean or from healthier stretches of beach. Each year, California coastal managers are moving three Rose Bowls’ worth of sand and spreading it out over eroding beaches, primarily in L.A. County.

But we’re losing ground in this battle. Coastal scientists say we’re only replenishing half of the sand that the beaches need to stay stable every year. UCLA’s Tony Orme is less than optimistic about California beaches' overall health.

"All this loss of beach is really due to our inappropriate use of beaches in the first place," Orme says.

Olena Yurchenko of Los Angeles comes to Venice Beach with her son every summer.

"[The] last ten years, this beach [is] much improved. Today we really enjoy it," she says, apologizing quickly before she runs into the surf toward her son. He's having too much fun to notice he’s getting into bigger waves.

Beach nourishment helps preserve the illusion that L.A. County’s beaches are completely natural. But the joy of a kid on a boogie board? That’s totally real.